…32 nChild (de)serialization

7fc487a refactor: use `{Read,Write}BE32` helpers for BIP32 nChild (de)serialization (Sebastian Falbesoner)

Pull request description:

  This small refactoring PR replaces manual bit-fiddling (de)serialization of the BIP32 child number (nChild) by the helpers `ReadBE32`/`WriteBE32`. Note that those were first introduced in dashpay#4100, almost one year _after_ the BIP32 derivation implementation has been merged (dashpay#2829, eb2c999).

ACKs for top commit:
  sipa:
    utACK 7fc487a
  laanwj:
    Code review ACK 7fc487a

Tree-SHA512: bbe3e411fb0429fa74c8a5705a91f4d6ed704dac9d6623ecb633563f22acf8e21f3189a16f1d0cf1aeedfc56a5b695df54ae51e9577e34eb6d7dc335de2da6de

* avoid deprecated C headers

* remove unused header

* typos

* unused include

* use static / const where possible

* make parameter const ref where possible

* Clang-Tidy: Parameter is passed by value and only copied once; consider moving it to avoid unnecessary copies

* Clang-Tidy: Passing result of std::move() as a const reference argument; no move will actually happen

* Clang-Tidy: Forwarding reference passed to std::move(), which may unexpectedly cause lvalues to be moved; use std::forward() instead

* access statically

…32 nChild (de)serialization

7fc487a refactor: use `{Read,Write}BE32` helpers for BIP32 nChild (de)serialization (Sebastian Falbesoner)

Pull request description:

  This small refactoring PR replaces manual bit-fiddling (de)serialization of the BIP32 child number (nChild) by the helpers `ReadBE32`/`WriteBE32`. Note that those were first introduced in dashpay#4100, almost one year _after_ the BIP32 derivation implementation has been merged (dashpay#2829, eb2c999).

ACKs for top commit:
  sipa:
    utACK 7fc487a
  laanwj:
    Code review ACK 7fc487a

Tree-SHA512: bbe3e411fb0429fa74c8a5705a91f4d6ed704dac9d6623ecb633563f22acf8e21f3189a16f1d0cf1aeedfc56a5b695df54ae51e9577e34eb6d7dc335de2da6de

…32 nChild (de)serialization

7fc487a refactor: use `{Read,Write}BE32` helpers for BIP32 nChild (de)serialization (Sebastian Falbesoner)

Pull request description:

  This small refactoring PR replaces manual bit-fiddling (de)serialization of the BIP32 child number (nChild) by the helpers `ReadBE32`/`WriteBE32`. Note that those were first introduced in dashpay#4100, almost one year _after_ the BIP32 derivation implementation has been merged (dashpay#2829, eb2c999).

ACKs for top commit:
  sipa:
    utACK 7fc487a
  laanwj:
    Code review ACK 7fc487a

Tree-SHA512: bbe3e411fb0429fa74c8a5705a91f4d6ed704dac9d6623ecb633563f22acf8e21f3189a16f1d0cf1aeedfc56a5b695df54ae51e9577e34eb6d7dc335de2da6de